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| Author(s): |
Sandro Luis Vatanabe
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Escola Politécnica (EP/BC) |
| Defense date: | 2012-11-09 |
| Examining board members: |
Emílio Carlos Nelli Silva;
Flávio Buiochi;
Jun Sérgio Ono Fonseca;
Gláucio Hermógenes Paulino;
Marcelo Areias Trindade
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| Advisor: | Emílio Carlos Nelli Silva |
| Abstract | |
Piezocomposite materials result from the combination of a piezoelectric material with other non-piezoelectric materials, offering advantages over conventional piezoelectric materials. Different effective properties can be obtained by changing the volume fraction of constituent materials, the shape of inclusions, or even the topology of the unit cell. Functionally Graded Materials (FGM) are composite materials, which are designed so that its composition varies gradually in space. One of the advantages of FGMs is that there is no conventional interface between the constituent materials, which reduces, for instance, microscopic stress concentration problems in composite materials. Topology Optimization Method (TOM) is a computational technique used to determine the material distribution of a structure or material in a systematic way, in order to maximize a determined objective function. Thus, this study proposes a generic and systematic methodology to design Functionally Graded Piezocomposites Materials (FGPM) using TOM, for quasi-static and dynamic applications. The study is divided into three groups. The first group combines the homogenization method with TOM in order to design FGPM for quasi-static applications, where the goal is to maximize the conversion of mechanical energy into electrical energy. The application used as an example in this study focuses materials used in energy harvesting devices. The second group focuses on dynamic applications of phononic piezocomposite materials, where the property of interest is the possibility of having frequency band gaps, in which elastic waves do not propagate. This study aims to design phononic FGPM with prescribed band gap width using one-dimensional model, and to design phononic FGPM with maximized band gaps using two-dimensional model. The third group investigates the pattern gradation concept, based on pattern repetitions over the design domain, but each pattern has one or more dimensions gradually modified. Thus, properties change gradually along the structure, although the material distribution keeps in the discrete form, thereby circumventing potential manufacturing difficulties. The objective function consists of maximizing the electric power generated in a load resistor. A projection scheme is employed to compute the element densities from design variables and control the length scale of the material density. Numerical examples are presented and discussed using the proposed methods. (AU) | |